1. Field of the Invention
The present invention relates to a fluid expandable drum for building portions of tires thereon and more particularly to a fluid expandable drum whose width is infinitely variable to enable the tire building drum to be utilized to build tires of various widths. The width of the tire building drum is controlled by a pair of piston members which move in a direction parallel to the axis of rotation of the drum in response to fluid pressure acting thereon to expand the width of the tire building surface. The fluid pressure acting on the pistons is the same fluid pressure which is available to expand the tube element.
Tire building drums including a fluid expandable tube element for expanding and contracting the diameter of a tire building surface are known in the art. The Woodhall U.S. Pat. No. 3,467,567 is an example of such a machine where the diameter of the building surface can be varied but the width of the building surface is fixed. It is also known to provide a building surface which can vary in width to facilitate the removal of a built tire therefrom. Such a machine is disclosed in the Heston U.S. Pat. No. 1,860,342 wherein a fluid actuatable piston is utilized to decrease the width of the tire building surface to facilitate the removal of a built tire portion therefrom. Heston does not provide a variable width building surface. Other prior art, not illustrated, discloses adding or subtracting drum segments to incrementally vary the width of the drum depending on the number of drum segments utilized. It is desirable to provide a tire building surface whose width taken parallel to the axis of rotation of the tire drum is infinitely variable and variable in response to fluid pressure to thereby control the width of the tire building surface.